Conventionally, as disclosed in Japanese patent documents 1 and 2, a vehicular air conditioner heats air, i.e., a blowing air to be sent into a vehicle compartment, by exchanging heat between the air (i.e., a third fluid) and a discharged refrigerant (i.e., a first fluid) discharged from a compressor. Further, the above documents 1, 2 further disclose a configuration that the vehicular air conditioner heats the blowing air by heat exchange between the blowing air and a heat medium that is different from the discharged refrigerant (i.e., a second fluid).
In other words, the vehicular air conditioner in the above documents 1, 2 uses a heat exchange system for exchanging heat between a plurality of fluids (i.e., a discharged refrigerant, a heat medium, and a blowing air). More practically, the heat exchange system is used as the one in which heat from two types of fluids (i.e., the first/second fluids) is transferred to the other fluid (i.e., the third fluid).
More practically, in the patent document 1, a heat exchange system for radiating heat from the discharged refrigerant and from a brine to the blowing air can be realized as a combined-type heat exchanger by combining two heat exchangers in one unit, that is, by combining a heating heat exchanger that heats the blowing air by the heat exchange between the blowing air and the discharged refrigerant and a heater core that heats the blowing air by the heat exchange between the blowing air and the brine that is a heat medium heated by a combustion-type heater.
Further, in the combined-type heat exchanger in the patent document 1, a temperature difference between the discharged refrigerant and the blowing air as well as a temperature difference between the brine and the blowing air are secured by positioning, on a downstream side of the heating heat exchanger in terms of the blowing air flowing therethrough, the heater core through which the brine having higher temperature than the discharged refrigerant is circulated.
Further, in the patent document 2, just like the disclosure in the patent document 1, a heat exchange system for radiating heat from the discharged refrigerant and from a coolant to the blowing air can be realized as a combined-type heat exchanger by combining two heat exchangers in one unit, that is, by combining a heating heat exchanger similar to the one in the patent document 1 and a heater core that heats the blowing air by the heat exchange between the blowing air and a coolant (i.e., a second fluid) for cooling an engine.
Further, in the combined-type heat exchanger in the patent document 2, a volume reduction for preventing a volume increase of an entire body of the heat exchanger is planned by combining a refrigerant tube and a coolant tube on their flat surfaces, i.e., by combining the refrigerant tube having a flat cross-section for passing the coolant through the heating heat exchanger and the coolant tube having a flat cross-section for passing the coolant through the heater core.